diff --git a/src/main/java/org/apache/commons/fileupload/FileUploadBase.java b/src/main/java/org/apache/commons/fileupload/FileUploadBase.java
index f8efb25..9e684e5 100644
--- a/src/main/java/org/apache/commons/fileupload/FileUploadBase.java
+++ b/src/main/java/org/apache/commons/fileupload/FileUploadBase.java
@@ -946,7 +946,7 @@
                     || (!contentType.toLowerCase(Locale.ENGLISH).startsWith(MULTIPART))) {
                 throw new InvalidContentTypeException(
                         format("the request doesn't contain a %s or %s stream, content type header is %s",
-                               MULTIPART_FORM_DATA, MULTIPART_FORM_DATA, contentType));
+                               MULTIPART_FORM_DATA, MULTIPART_MIXED, contentType));
             }
 
             InputStream input = ctx.getInputStream();